MaaT Pharma has submitted a marketing authorisation application (MAA) to the European Medicines Agency (EMA) for its lead candidate Xervyteg (MaaT013), a microbiota-based therapy for acute graft-versus-host disease (aGvHD) in patients who have received two previous lines of treatment.

If approved, Xervyteg would become the first microbiota therapeutic authorized by the EMA and the first globally in a hemato-oncology indication. It would also be the first approved therapy specifically for aGvHD with gastrointestinal involvement following failure of both steroid and ruxolitinib treatments—an area with no approved third-line therapies to date.

The submission is based on data from the pivotal ARES trial, a European, multicenter, open-label, single-arm study that assessed the safety and efficacy of Xervyteg in 66 adults with gastrointestinal aGvHD. The study met its primary endpoint, with a gastrointestinal overall response rate of 62% at Day 28, surpassing the expected rate of 38%. An overall response rate across all affected organs was reported at 64%. The majority of patients who responded experienced full resolution of clinical symptoms.

A 12-month survival probability of 54% was observed, with responders at Day 28 showing a significantly higher survival rate (67%) compared to non-responders (28%). The company said these outcomes suggest a potential survival benefit linked to early clinical response. Supporting data from 186 patients treated through the company’s ongoing early access programme (EAP) across Europe and the US were also included in the application.

“Submitting our MAA to the EMA marks a major regulatory milestone for MaaT Pharma and a meaningful advancement for patients with refractory aGvHD—a life-threatening complication of stem cell transplantation with no approved therapies,” said Hervé Affagard, co-founder and CEO of MaaT Pharma.

“We are now closer to providing a much-needed treatment option and remain deeply committed to advancing immunomodulating microbiota technologies in hemato-oncology, where new solutions are urgently needed.”

Safety data from both the ARES study and the EAP were reviewed by an independent data safety monitoring board (DSMB), which concluded in March 2025 that the safety profile was acceptable and supported a favorable benefit-risk balance. The DSMB will continue to monitor safety until all patients reach one-year follow-up.

MaaT Pharma said demand for Xervyteg through its EAP rose by 75% in 2024 compared to the previous year. In France, where the program was first launched, the company said it had captured around 25% of the addressable patient population. These figures suggest growing recognition of the therapy’s clinical potential.

aGvHD remains a severe complication following allogeneic stem cell transplantation and is often resistant to currently available treatments. The median survival for patients who fail both first- and second-line therapies is just 28 days, with one-year mortality rates reaching 85%, according to a 2021 study by Abedin and colleagues.

The EMA will now review the application under the centralized procedure. If approved, the authorization would cover all EU member states and the European Economic Area countries. A potential launch could take place in 2026, subject to regulatory approval. MaaT Pharma is currently in discussions with prospective strategic partners to support the commercial rollout.